A euphemism is a term or a phrase used by individuals to refer to a controversial topic as overwhelmingly inoffensive as possible, as opposed to being
politically incorrect (aka "enthusiastically offensive").
Unfortunately, the overuse of a euphemism will eventually devolve its
meaning to the extent that itself becomes
politically incorrect and will have to be replaced with another euphemism. This is a sociolinguistic phenomenon to as the "euphemism treadmill".
The term "mental retardation" was once a euphemism and politically correct term used to describe stupidity. The previous term was imbecile which was an actual medical category which comprised of idiots (
IQ 0 to 25), imbeciles (
IQ 26 to 50), and morons (
IQ 51 to 70).
Over time, mental retardation and its associated verb "
retard" became as corrupted as "imbecile" and "
idiot" and was eventually replaced with "intellectual disability". It is now only a matter of time when being "disabled" is offensive and once again, slides down the euphemism treadmill.